Conventional gas turbine engines include a fan section and a core engine with the fan section having a larger outer diameter than that of the core engine. The fan section and the core engine are disposed sequentially about a longitudinal axis and are enclosed in a nacelle. An annular path of primary airflow passes through the fan section and the core engine to generate primary thrust. An annular path of duct or fan flow, disposed radially outward of the primary airflow path, passes through the fan section and exits through a fan nozzle to generate fan thrust.
After touch down, a thrust reverser is activated to slow down the aircraft. The thrust reverser slows down the aircraft by preventing the gas turbine engine from generating forward fan thrust and by generating reverse thrust to counteract primary forward thrust. The thrust reverser is disposed in the downstream portion of the nacelle and comprises a translating sleeve and a blocker door, each having a stowed and a deployed position. In the stowed position, the blocker door is disposed in a substantially parallel relationship to the longitudinal axis of the engine. Upon actuation, the blocker door swings into the deployed position to block the fan flow path, thereby preventing the fan flow from generating the forward fan thrust. Upon actuation, the translating sleeve slides axially downstream into the deployed position to expose a plurality of cascades. Each cascade includes a plurality of turning vanes to guide the fan flow. Since the blocker door blocks the path of the fan flow, substantially the entire fan flow is diverted through the cascades. The turning vanes turn the fan flow to generate reverse thrust that counteracts the forward primary thrust.
The newer generations of gas turbine engines tend to have longer fan blades that generate a greater volume of fan flow, consequently resulting in greater fan thrust. The thrust reversers of these newer engines must be proportionally larger in order to accommodate the larger volume of fan flow and the wider fan flow path. Specifically, the blocker door must be fabricated to be longer to span the wider fan flow path. Also, the cascade must be fabricated to be longer in order to accommodate the larger volume of the fan flow that is being diverted. The longer cascade dictates the use of a longer translating sleeve that slides on a longer set of tracks and is activated by a longer set of actuators. The additional length of the hardware translates into a heavier gas turbine engine. As is well known in the art, the extra weight adversely effects the overall performance of the aircraft. The additional weight induces extra drag which results in additional fuel consumption for operation of the engine. Therefore, it is the primary objective in gas turbine engine fabrication to avoid a weight increase therein.